Sandip Ghosh

Stability analysis for continuous system with additive time-varying delays: A less conservative result

This paper presents a less conservative result for stability analysis of continuous-time systems with additive delays by constructing a new Lyapunov-Krasovskii functional and utilizing free matrix variables in approximating certain integral quadratic terms in obtaining the stability condition in terms of linear matrix inequalities. Numerical example is provided to show the effectiveness of the proposed method compared to some recent results.

Decentralized Stabilization of Uncertain Systems With Interconnection and Feedback Delays: An LMI Approach

This note presents a broad LMI condition that can ascertain the stability of uncertain systems under decentralized feedback in the presence of interconnection and feedback delays. Based on the Lyapunovs direct approach with a four-term energy functional and a three-term quadratic formulation of the given state dynamics, this method has a larger search space than used so far. Numerical examples corroborate the superiority of this method vis-a-vis the existing ones for several subsets of the general problem.

State feedback stabilization of uncertain linear time‐delay systems: A nonlinear matrix inequality approach

A nonlinear matrix inequality is derived as a stabilizability condition of linear uncertain time-delay systems. This inequality is seen as a less conservative one as well as efficient for numerical computation than the existing results as seen when solving by cone-complementary algorithm. Copyright

An improved robust stability analysis for systems with two delays by extracting overlapping feature

In this paper, a delay-dependent robust stability criterion is proposed for linear systems with two delays. For delay-dependent stable systems, the delays are very small in nature. So, they may overlap each other. This overlapping information may be exploited to obtain a less conservative criterion. To extract such information, a special type of simple Lyapunov–Krasovskii functional is considered. To derive the criterion in form of Linear Matrix inequalities, a matrix variable approach is used. Some numerical examples are presented to validate the less conservativeness of the proposed criterion.

Improved delay-range-dependent stability analysis of a time-delay system with norm bounded uncertainty.

This paper presents improved robust delay-range-dependent stability analysis of an uncertain linear time-delay system following two different existing approaches - (i) non-delay partitioning (NDP) and (ii) delay partitioning (DP). The derived criterion (for both the approaches) proposes judicious use of integral inequality to approximate the uncertain limits of integration arising out of the time-derivative of Lyapunov-Krasovskii (LK) functionals to obtain less conservative results. Further, the present work compares both the approaches in terms of relative merits as well as highlights tradeoff for achieving higher delay bound and (or) reducing number of decision variables without losing conservatism in delay bound results. The analysis and discussion presented in the paper are validated by considering relevant numerical examples.

Stability analysis of linear systems with two delays of overlapping ranges

In this paper, a delay-dependent stability criterion is derived for linear time-delay systems with two constant delays having overlapping ranges. This overlapping feature of the delays is exploited in delay-dependent analysis of the system using Lyapunov-Krasovskii approach. The developed treatment of the delays reduces conservatism in analysis compared to the approaches treating the delays individually. Numerical examples are used to demonstrate the less conservativeness of the derived criterion.

Active sway control of a single pendulum gantry crane system using output-delayed feedback control technique

This paper investigates the implementation of output-delayed feedback control (ODFC) technique for controlling the sway angle of single pendulum gantry crane (SPGC) system. Linearized mathematical model of the SPGC in state space form is considered for the investigation. The designed ODFC has undergone complete stability analysis for a given controller gain.

On delay robustness improvement using digital Smith predictor for networked control systems

Abstract This paper presents a study on delay robustness improvement ability of a digital Smith predictor based delay compensator for networked control systems with bounded network induced time-varying delays and packet losses. The compensator is considered to be implemented in digital form with time-driven controller and event-driven actuator configuration. The uncertain system model is represented in polytopic form and Lyapunov method is used for stability analysis in terms of linear matrix inequalities. The performance of the digital predictor in terms of delay-tolerability is then tested on two numerical examples and verified with simulation using TrueTime simulator. It is found that the selection of predictor delay can be made based on bounds of network delays to improve the performance of the controller.

Tolerable delay-margin improvement for systems with input–output delays using dynamic delayed feedback controllers

Abstract This paper presents investigations on a dynamic state feedback controller with state delays that improves tolerable delay margin for systems with input–output delays. Using an iterative pole placement technique for time-delay systems, the effect of introducing state delay in the controller dynamics is studied. It is observed that such a controller improves the tolerable delay margins compared to its static or even simple dynamic counterpart.

Robust Analysis of Networked Control Systems with Time-Varying Delays

Abstract In this paper, a comparison of polytopic and norm-bounded approach is sought for stability analysis of networked control systems (NCS) with uncertain time-varying delays. The delays are considered to be general in the sense that these could be either smaller or greater than the sampling time. For stability analysis, first the continuous-time NCS plant is represented remodeled into an equivalent discrete time one. The uncertainties in the NCS model arises due to the time varying delays are modeled using both polytopic and norm-bounded approach. Considering a state-feedback controller, LMI conditions are used to exploit the stability region in the controller and delay parameter plane using two numerical examples. It is observed that the norm-bounded (NB) approach is slightly conservative whereas higher computational complexities are involved in the polytopic one.